Articulated roller chain conveyors are commonly used in packaging applications to convey articles such as bottles or cans through a packaging machine to be loaded into paperboard cartons. It is often the practice to attach plates to the roller chain or to interlock plates to provide a smooth surface upon which the articles and/or cartons are conveyed. It is important to prevent the conveyor surface from tilting, buckling, or excessively undulating, which topples articles, interferes with other packaging machine components such as lane dividers, damages carton flaps, or otherwise causes misfeeds. This problem is exacerbated when accessories such as lugs are mounted to the plates to facilitate grouping or metering of articles. Each lug extends outward with respect to the surface of the plate to which it is mounted and increases the tendency of the plate to rotate about its longitudinal access (i.e., the lug increases the moment of the plate about a horizontal axis parallel to the direction of flow). Prior art lugs commonly shear off when exposed to these forces, as the lugs are often secured by two screws or pins disposed through the surface of the plate. The pins concentrate the reaction loads in singular areas of the plastic chain top, and thus, have the tendency to snap causing the lug to disengage. Such failures are costly, as the affected plate must be replaced or the broken screw or pins removed to mount another lug. It is desirable, therefore, to have plates that resist this moment and provide a stable surface regardless of whether accessories are mounted.
One prior approach that has been taken to reduce tilting, buckling, or excessive undulation of packaging machine conveyors involves running the transport chain under relatively high tension. This approach disadvantageously exposes the transport chain to increased wear and to elongation over time, particularly, as the transport chains are commonly constructed using links formed from plastic that are interlocked with steel pins.
Transport chains also typically comprise a single base chain disposed centrally with respect to the surface of the conveyor belt. Such single chain arrangements provide little resistance to rotational forces, and are more susceptible to stretching and other damage that can be caused by such forces as well as by typical operating conditions.
What is needed is a conveyor belt having a substantially flat, stable surface that resists tilting, buckling, and excessive motion. There is also a need for a durable transport chain that contributes to the stability of the conveyor belt without diminishing the efficiency of the machine. What is further needed is a conveyor plate upon which a grouping lug or other member can be securely mounted, and that is easily detachable for replacement or repair, or to reconfigure the conveyor belt.